1. Field of the Invention
This invention relates to power MOSFET devices and more particularly to an improved design of such devices.
2. Description of Related Art
In current power MOSFET devices, in order to reduce the surface breakdown voltage, inclusion in the device of a thin diffused layer is required. The thin diffused layer results in the increase of "ON-resistance" because the width of the conduction path is reduced by this thin diffused layer. "ON-resistance", as employed here, refers to the resistance of the device when it is turned on. The breakdown occurs at a surface which requires less electrical field than the bulk of the semiconductor. The breakdown leads to a lowered dynamic resistance and higher currents. For high voltage device designs, the surface breakdown condition should be avoided.
U.S. Pat. No. 5,019,522 of Meyer et al shows a power transistor and methods for making that transistor.